Interplay between HDAC3 and WDR5 is essential for hypoxia-induced epithelial-mesenchymal transition

Reciprocal Modulation of Tumour and Immune Cell Motility: Uncovering Dynamic Interplays and Therapeutic Approaches

Dysregulated cell movement is a hallmark of cancer progression and metastasis, the leading cause of cancer-related mortality. The metastatic cascade involves tumour cell migration, invasion, intravasation, dissemination, and colonisation of distant organs. These processes are influenced by reciprocal interactions between cancer cells and the tumour microenvironment (TME), including immune cells, stromal components, and extracellular matrix proteins. The epithelial-mesenchymal transition (EMT) plays a crucial role in providing cancer cells with invasive and stem-like properties, promoting dissemination and resistance to apoptosis. Conversely, the mesenchymal-epithelial transition (MET) facilitates metastatic colonisation and tumour re-initiation. Immune cells within the TME contribute to either anti-tumour response or immune evasion. These cells secrete cytokines, chemokines, and growth factors that shape the immune landscape and influence responses to immunotherapy. Notably, immune checkpoint blockade (ICB) has transformed cancer treatment, yet its efficacy is often dictated by the immune composition of the tumour site. Elucidating the molecular cross-talk between immune and cancer cells, identifying predictive biomarkers for ICB response, and developing strategies to convert cold tumours into immune-active environments is critical to overcoming resistance to immunotherapy and improving patient survival.

HBO1 determines epithelial-mesenchymal transition and promotes immunotherapy resistance in ovarian cancer cells

PURPOSE

Epithelial-mesenchymal transition (EMT) plays critical roles in tumor progress and treatment resistance of ovarian cancer (OC), resulting in the most deadly gynecological cancer in women. However, the cell-intrinsic mechanism underlying EMT in OC remains less illuminated.

METHOD

SKOV3, the OC cell line, was treated with TGF-β to induce EMT or with SB431542, an inhibitor of the TGF-β signaling pathway, to reduce migration. The function of HBO1 in EMT was confirmed by knock-down or overexpression of HBO1 in SKOV3 cells. The role of HBO1 in cell proliferation and apoptosis of SKOV3 cells was analyzed by flow cytometry. The whole-genome transcriptome was used to compare significantly different genes in control and HBO1-KD SKOV3 cells. T-cell cytotoxicity assays were measured by an IVIS spectrum. The chromatin binding of HBO1 was investigated using CUT&Tag-seq.

RESULTS

Here, we show that HBO1, a MYST histone acetyltransferase (HAT), is a cell-intrinsic determinant for EMT in OC cells. HBO1 is greatly elevated during TGF-β-triggered EMT in SKOV3 OC cells as well as in later stages of clinical OC samples. HBO1 Knock-down (KD) in SKOV3 cells blocks TGF-β-triggered EMT, migration, invasion and tumor formation in vivo. Interestingly, HBO1 KD in SKOV3 cells suppresses their resistance to CAR-T cells. Mechanistically, HBO1 co-binds the gene sets responsible for EMT with SMAD4 and orchestrates a gene regulatory network critical for tumor progression in SKOV3 cells.

CONCLUSION

HBO1 plays an essential onco-factor to drive EMT and promote the immunotherapy resistance in ovarian cancer cells. Together, we reveal a critical role of HBO1 mediated epigenetic mechanism in OC progression, providing an insight into designing new therapy strategies.

HDAC3 and Snail2 complex promotes melanoma metastasis by epigenetic repression of IGFBP3

The treatment of metastatic melanoma has long posed a complex challenge within clinical practice. Previous studies have found that EMT transcription factors are essential in the development of various cancers through their induction of EMT. Here, we demonstrate that Snail2 expression is dramatically increased in melanoma and is associated with an adverse prognosis. Elevated Snail2 in melanoma cells enhanced migratory and invasive capabilities in vitro and in vivo. Furthermore, RNA-Seq analysis revealed a significant reduction of IGFBP3 expression in melanoma cells overexpressing Snail2. IGFBP3 might mitigate the Snail2's ability to promote melanoma metastasis via the PI3K-AKT pathway. Moreover, Snail2 and HDAC3 collaborate to suppress IGFBP3 transcription through H3K4 deacetylation and H4K5 delactylation. Additionally, the combination of HDAC3 and p-GSK-3β inhibitors significantly improved the treatment outcomes for lung metastasis in melanoma in vivo. The results of our study indicate that Snail2, HDAC3, and IGFBP3 play significant roles in melanoma progression and represent promising therapeutic targets.

The plasticity of epithelial cells and its potential in the induced differentiation of gastric cancer

Cell plasticity refers to the deviation of cells from normal terminal differentiation states when faced with environmental and genetic toxic stresses, resulting in the phenomenon of transforming into other cell or tissue phenotypes. Unlocking phenotype plasticity has been defined as a hallmark of malignant tumors. The stomach is one of the organs in the body with the highest degree of self-renewal and exhibits significant cell plasticity. In this paper, based on the review of the characteristics of normal differentiation of gastric epithelial cells and their markers, the four main phenotypes of gastric epithelial cell remodeling and their relationship with gastric cancer (GC) are drawn. Furthermore, we summarize the regulatory factors and mechanisms that affect gastric epithelial cell plasticity and outline the current status of research and future prospection for the treatment targeting gastric epithelial cell plasticity. This study has important theoretical reference value for the in-depth exploration of epithelial cell plasticity and the tumor heterogeneity caused by it, as well as for the precise treatment of GC.

BRD3308 suppresses macrophage oxidative stress and pyroptosis via upregulating acetylation of H3K27 in sepsis-induced acute lung injury

Background

Sepsis-induced acute lung injury (ALI) leads to severe hypoxemia and respiratory failure, contributing to poor prognosis in septic patients. Endotoxin dissemination triggers oxidative stress and the release of inflammatory cytokines in macrophages, initiating diffuse alveolar damage. The role of epigenetic histone modifications in organ injury is increasingly recognized. The present study aimed to investigate the use of a histone modification inhibitor to alleviate sepsis-induced ALI, revealing a new strategy for improving sepsis patient survival.

Methods

In vivo models of ALI were established through the intraperitoneal injection of lipopolysaccharide and cecal ligation and puncture surgery. Furthermore, the disease process was simulated in vitro by stimulating Tamm-Horsfall protein-1 (THP-1) cells with lipopolysaccharide. Hematoxylin and eosin staining, blood gas analysis and pulmonary function tests were utilized to assess the extent of lung tissue damage. Western blot analysis, real-time polymerase chain reaction, enzyme-linked immunosorbent assay and immunofluorescence were used to measure the levels and distribution of the indicated indicators within cells and tissues. Reactive oxygen species and autophagic flux alterations were detected using specific probes.

Results

BRD3308, which is a inhibitor of histone deacetylase 3, improved lung tissue damage, inflammatory infiltration and edema in ALI by inhibiting Nod-like receptor protein3-mediated pyroptosis in macrophages. By upregulating autophagy, BRD3308 improved the disruption of redox balance in macrophages and reduced the accumulation of reactive oxygen species. Mechanistically, BRD3308 inhibited histone deacetylase 3 activity by binding to it and altering its conformation. Following histone deacetylase 3 inhibition, acetylation of H3K27 was significantly increased. Moreover, the increase in H3K27Ac led to the upregulation of autophagy-related gene 5, a key component of autophagosomes, thereby activating autophagy.

Conclusions

BRD3308 inhibits oxidative stress and pyroptosis in macrophages by modulating histone acetylation, thereby preventing sepsis-induced ALI. The present study provides a potential strategy and theoretical basis for the clinical treatment of sepsis-induced ALI.

PRM1201 effectively inhibits colorectal cancer metastasis via shaping gut microbiota and short- chain fatty acids

BACKGROUND

PRM1201 is a traditional medicine with beneficial effects against colorectal cancer (CRC) metastasis. However, the underlying mechanism of this action remains to be determined.

HYPOTHESIS

Remodeling microbiota and short-chain fatty acids (SCFAs) metabolism might be a potential mechanism to explain the anti-metastatic action of PRM1201, as this gut-microbiota dependent effect involves downregulation of histone deacetylation and EMT.

METHODS

To investigate this possibility, clinical specimens were sequenced and the correlation between the anti-metastatic efficacy of PRM1201 and the restoration of SCFA-producing bacteria was studied. To obtain solid causal evidence, a mouse metastasis model was established to detect the influence of PRM1201 on cancer metastasis. Specifically, 16S amplicon sequencing, ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis, and bacterial manipulation were used to examine the gut microbiota-driven anti-metastatic action of PRM1201.

RESULTS

Clinical data showed that PRM1201 increased both the number of SCFA-producing bacteria and generation of SCFAs in the feces of CRC patients. A positive correlation between the anti-metastatic efficacy of PRM1201 and the restoration of SCFAs observed. The animal experiments demonstrated that PRM1201 effectively blocked CRC metastasis in a dose-dependent manner. PRM1201 treatment modulated the composition of gut microbiota, and promoted the proliferation of beneficial SCFAs producers such as Akkermansia, Lachnospiraceae_NK4A136_group and Blautia, while simultaneously reducing the abundance of pathogenic bacteria like Escherichia-Shigella. In addition, PRM1201 led to augmentation of SCFAs content. Further results indicated that the anti-cancer metastatic mechanism of PRM1201 was linked to inhibition of histone deacetylation and suppression of epithelial-to-mesenchymal transition (EMT) in metastatic lesions. Microbiota depletion treatment and fecal microbiota transplantation (FMT) underscored the microbiota-dependent nature of this phenomenon. Moreover, this anti-colorectal cancer metastatic effect and mechanism of total SCFAs and single SCFA were also confirmed.

CONCLUSION

In summary, PRM1201 exerts its anti-metastatic effects by modulating SCFA-producing bacteria and enhancing the production of SCFAs. Furthermore, the prebiotic-like actions of PRM1201, along with the PRM1201-treated bacteria, function as inhibitors of histone deacetylases (DHACs) thereby effectively suppressing EMT events.

The cellular-centered view of hypoxia tumor microenvironment: Molecular mechanisms and therapeutic interventions

Cancer is a profoundly dynamic, heterogeneous and aggressive systemic ailment, with a coordinated evolution of various types of tumor niches. Hypoxia plays an indispensable role in the tumor micro-ecosystem, drastically enhancing the plasticity of cancer cells, fibroblasts and immune cells and orchestrating intercellular communication. Hypoxia-induced signals, particularly hypoxia-inducible factor-1α (HIF-1α), drive the reprogramming of genetic, transcriptional, and proteomic profiles. This leads to a spectrum of interconnected processes, including augmented survival of cancer cells, evasion of immune surveillance, metabolic reprogramming, remodeling of the extracellular matrix, and the development of resistance to conventional therapeutic modalities like radiotherapy and chemotherapy. Here, we summarize the latest research on the multifaceted effects of hypoxia, where a multitude of cellular and non-cellular elements crosstalk with each other and co-evolve in a synergistic manner. Additionally, we investigate therapeutic approaches targeting hypoxic niche, encompassing hypoxia-activated prodrugs, HIF inhibitors, nanomedicines, and combination therapies. Finally, we discuss some of the issues to be addressed and highlight the potential of emerging technologies in the treatment of cancer.

Hypoxia-induced CTCF promotes EMT in breast cancer

Cancer cells experiencing hypoxic stress employ epithelial-mesenchymal transition (EMT) to undergo metastasis through rewiring of the chromatin landscape, epigenetics, and importantly, gene expression. Here, we showed that hypoxia modulates the epigenetic landscape on CTCF promoter and upregulates its expression. Hypoxia-driven epigenetic regulation, specifically DNA demethylation mediated by TET2, is a prerequisite for CTCF induction. Mechanistically, in hypoxic conditions, Hypoxia-inducible factor 1-alpha (HIF1α) binds to the unmethylated CTCF promoter, causing transcriptional upregulation. Further, we uncover the pivotal role of CTCF in promoting EMT as loss of CTCF abrogated invasiveness of hypoxic breast cancer cells. These findings highlight the functional contribution of HIF1α-CTCF axis in promoting EMT in hypoxic breast cancer cells. Lastly, CTCF expression is alleviated and the potential for EMT is diminished when the HIF1α binding is particularly disrupted through the dCas9-DNMT3A system-mediated maintenance of DNA methylation on the CTCF promoter. This axis may offer a unique therapeutic target in breast cancer.

Initial Characterization of WDR5B Reveals a Role in the Proliferation of Retinal Pigment Epithelial Cells

The chromatin-associated protein WDR5 has been widely studied due to its role in histone modification and its potential as a pharmacological target for the treatment of cancer. In humans, the protein with highest sequence homology to WDR5 is encoded by the retrogene WDR5B, which remains unexplored. Here, we used CRISPR-Cas9 genome editing to generate WDR5B knockout and WDR5B-FLAG knock-in cell lines for further characterization. In contrast to WDR5, WDR5B exhibits low expression in pluripotent cells and is upregulated upon neural differentiation. Loss or shRNA depletion of WDR5B impairs cell growth and increases the fraction of non-viable cells in proliferating retinal pigment epithelial (RPE) cultures. CUT&RUN chromatin profiling in RPE and neural progenitors indicates minimal WDR5B enrichment at established WDR5 binding sites. These results suggest that WDR5 and WDR5B exhibit several divergent biological properties despite sharing a high degree of sequence homology.

A Histone Methylation-MAPK Signaling Axis Drives Durable Epithelial-Mesenchymal Transition in Hypoxic Pancreatic Cancer

The tumor microenvironment in pancreatic ductal adenocarcinoma (PDAC) plays a key role in tumor progression and response to therapy. The dense PDAC stroma causes hypovascularity, which leads to hypoxia. Here, we showed that hypoxia drives long-lasting epithelial-mesenchymal transition (EMT) in PDAC primarily through a positive-feedback histone methylation-MAPK signaling axis. Transformed cells preferentially underwent EMT in hypoxic tumor regions in multiple model systems. Hypoxia drove a cell autonomous EMT in PDAC cells, which, unlike EMT in response to growth factors, could last for weeks. Furthermore, hypoxia reduced histone demethylase KDM2A activity, suppressed PP2 family phosphatase expression, and activated MAPKs to post-translationally stabilize histone methyltransferase NSD2, leading to an H3K36me2-dependent EMT in which hypoxia-inducible factors played only a supporting role. Hypoxia-driven EMT could be antagonized in vivo by combinations of MAPK inhibitors. Collectively, these results suggest that hypoxia promotes durable EMT in PDAC by inducing a histone methylation-MAPK axis that can be effectively targeted with multidrug therapies, providing a potential strategy for overcoming chemoresistance.

SIGNIFICANCE

Integrated regulation of histone methylation and MAPK signaling by the low-oxygen environment of pancreatic cancer drives long-lasting EMT that promotes chemoresistance and shortens patient survival and that can be pharmacologically inhibited. See related commentary by Wirth and Schneider, p. 1739.

Histone H3K4ac, as a marker of active transcription start sites and enhancers, plays roles in histone eviction and RNA transcription

The lysine 4 of histone H3 (H3K4) can be methylated or acetylated into four states: H3K4me1, H3K4me2, H3K4me3, or H3K4ac. Unlike H3K4 methylation, the genome-wide distribution and functional roles of H3K4ac remain unclear. To understand the relationship of acetylation with methylation at H3K4 and to explore the roles of H3K4ac in the context of chromatin, we analyzed H3K4ac across the human genome and compared it with H3K4 methylation in K562 cells. H3K4ac was positively correlated with H3K4me1/2/3 in reciprocal analysis. A decrease in H3K4ac through the mutation of the histone acetyltransferase p300 reduced H3K4me1 and H3K4me3 at the H3K4ac peaks. H3K4ac was also impaired by H3K4me depletion in the histone methyltransferase MLL3/4-mutated cells. H3K4ac peaks were enriched at enhancers in addition to the transcription start sites (TSSs) of genes. H3K4ac of TSSs and enhancers was positively correlated with mRNA and eRNA transcription. A decrease in H3K4ac reduced H3K4me3 and H3K4me1 in TSSs and enhancers, respectively, and inhibited the eviction of histone H3 from them. The mRNA transcription of highly transcribed genes was affected by the reduced H3K4ac. Interestingly, H3K4ac played a redundant role with regard to H3K27ac in eRNA transcription. These results indicate that H3K4ac serves as a marker of both active TSSs and enhancers and plays a role in histone eviction and RNA transcription by leading to H3K4me1/3.

Deciphering the interplay of histone post-translational modifications in cancer: Co-targeting histone modulators for precision therapy

Chromatin undergoes dynamic regulation through reversible histone post-translational modifications (PTMs), orchestrated by "writers," "erasers," and "readers" enzymes. Dysregulation of these histone modulators is well implicated in shaping the cancer epigenome and providing avenues for precision therapies. The approval of six drugs for cancer therapy targeting histone modulators, along with the ongoing clinical trials of numerous candidates, represents a significant advancement in the field of precision medicine. Recently, it became apparent that histone PTMs act together in a coordinated manner to control gene expression. The intricate crosstalk of histone PTMs has been reported to be dysregulated in cancer, thus emerging as a critical factor in the complex landscape of cancer development. This formed the foundation of the swift emergence of co-targeting different histone modulators as a new strategy in cancer therapy. This review dissects how histone PTMs, encompassing acetylation, phosphorylation, methylation, SUMOylation and ubiquitination, collaboratively influence the chromatin states and impact cellular processes. Furthermore, we explore the significance of histone modification crosstalk in cancer and discuss the potential of targeting histone modification crosstalk in cancer management. Moreover, we underscore the significant strides made in developing dual epigenetic inhibitors, which hold promise as emerging candidates for effective cancer therapy.

Hypoxia-inducible PRMT2 addiction in glioblastomas

Hypoxia-inducible transcription factors (HIFs) are key transcription factors for cellular response to low oxygen levels. However, the specific mediators responsible for activating downstream transcription are not well characterized. We previously identified Protein Arginine methyltransferase 2 (PRMT2), a highly expressed methyltransferase in glioblastoma multiforme, as a transcription co-activator. And we established a connection between PRMT2-mediated histone H3R8 asymmetric methylation (H3R8me2a) and transcription activation. Here we find that PRMT2 is activated by HIF1α under hypoxic conditions. And we demonstrate that PRMT2 and its H3R8me2a activity are required for the transcription activation of a significant subset of hypoxia-induced genes. Consequently, the inactivation of PRMT2 suppresses hypoxia-induced glioblastoma cell migration, attenuates tumor progression, and enhances chemotherapeutic sensitivity in mouse xenograft models. In addition, our analysis of clinical glioma specimens reveals a correlation between PRMT2 protein levels, HIF1α abundance, and an unfavorable prognosis. Our study establishes HIF1α-induced PRMT2 as a critical modulator in the activation of hypoxia-related transcriptional programs, ultimately driving malignant progression.

Effect of plasma exosome lncRNA on isoproterenol hydrochloride-induced cardiotoxicity in rats

Isoprenaline hydrochloride (IH) is a β-adrenergic receptor agonist commonly used in the treatment of hypotension, shock, asthma, and other diseases. However, IH-induced cardiotoxicity limits its application. A large number of studies have shown that long noncoding RNA (lncRNA) regulates the occurrence and development of cardiovascular diseases. This study aimed to investigate whether abnormal lncRNA expression is involved in IH-mediated cardiotoxicity. First, the Sprague-Dawley (SD) rat myocardial injury model was established. Circulating exosomes were extracted from the plasma of rats and identified. In total, 108 differentially expressed (DE) lncRNAs and 150 DE mRNAs were identified by sequencing. These results indicate that these lncRNAs and mRNAs are substantially involved in chemical cardiotoxicity. Further signaling pathway and functional studies indicated that lncRNAs and mRNAs regulate several biological processes, such as selective mRNA splicing through spliceosomes, participate in sphingolipid metabolic pathways, and play a certain role in the circulatory system. Finally, we obtained 3 upregulated lncRNAs through reverse transcription-quantitative PCR (RT-qPCR) verification and selected target lncRNA-mRNA pairs according to the regulatory relationship of lncRNA/mRNA, some of which were associated with myocardial injury. This study provides valuable insights into the role of lncRNAs as novel biomarkers of chemical-induced cardiotoxicity.

Epigenetic Regulation of EMP/EMT-Dependent Fibrosis

Fibrosis represents a process characterized by excessive deposition of extracellular matrix (ECM) proteins. It often represents the evolution of pathological conditions, causes organ failure, and can, in extreme cases, compromise the functionality of organs to the point of causing death. In recent years, considerable efforts have been made to understand the molecular mechanisms underlying fibrotic evolution and to identify possible therapeutic strategies. Great interest has been aroused by the discovery of a molecular association between epithelial to mesenchymal plasticity (EMP), in particular epithelial to mesenchymal transition (EMT), and fibrogenesis, which has led to the identification of complex molecular mechanisms closely interconnected with each other, which could explain EMT-dependent fibrosis. However, the result remains unsatisfactory from a therapeutic point of view. In recent years, advances in epigenetics, based on chromatin remodeling through various histone modifications or through the intervention of non-coding RNAs (ncRNAs), have provided more information on the fibrotic process, and this could represent a promising path forward for the identification of innovative therapeutic strategies for organ fibrosis. In this review, we summarize current research on epigenetic mechanisms involved in organ fibrosis, with a focus on epigenetic regulation of EMP/EMT-dependent fibrosis.

Epigenetic alterations fuel brain metastasis via regulating inflammatory cascade

Brain metastasis (BrM) is a major threat to the survival of melanoma, breast, and lung cancer patients. Circulating tumor cells (CTCs) cross the blood-brain barrier (BBB) and sustain in the brain microenvironment. Genetic mutations and epigenetic modifications have been found to be critical in controlling key aspects of cancer metastasis. Metastasizing cells confront inflammation and gradually adapt in the unique brain microenvironment. Currently, it is one of the major areas that has gained momentum. Researchers are interested in the factors that modulate neuroinflammation during BrM. We review here various epigenetic factors and mechanisms modulating neuroinflammation and how this helps CTCs to adapt and survive in the brain microenvironment. Since epigenetic changes could be modulated by targeting enzymes such as histone/DNA methyltransferase, deacetylases, acetyltransferases, and demethylases, we also summarize our current understanding of potential drugs targeting various aspects of epigenetic regulation in BrM.

Overlapping characteristics of weak interactions of two transcriptional regulators with WDR5

The WD40 repeat protein 5 (WDR5) is a nuclear hub that critically influences gene expression by interacting with transcriptional regulators. Utilizing the WDR5 binding motif (WBM) site, WDR5 interacts with the myelocytomatosis (MYC), an oncoprotein transcription factor, and the retinoblastoma-binding protein 5 (RbBP5), a scaffolding element of an epigenetic complex. Given the clinical significance of these protein-protein interactions (PPIs), there is a pressing necessity for a quantitative assessment of these processes. Here, we use biolayer interferometry (BLI) to examine interactions of WDR5 with consensus peptide ligands of MYC and RbBP5. We found that both interactions exhibit relatively weak affinities arising from a fast dissociation process. Remarkably, live-cell imaging identified distinctive WDR5 localizations in the absence and presence of full-length binding partners. Although WDR5 tends to accumulate within nucleoli, WBM-mediated interactions with MYC and RbBP5 require their localization outside nucleoli. We utilize fluorescence resonance energy transfer (FRET) microscopy to confirm these weak interactions through a low FRET efficiency of the MYC-WDR5 and RbBP5-WDR5 complexes in living cells. In addition, we evaluate the impact of peptide and small-molecule inhibitors on these interactions. These outcomes form a fundamental basis for further developments to clarify the multitasking role of the WBM binding site of WDR5.

Environmental factor reversibly determines cellular identity through opposing Integrators that unify epigenetic and transcriptional pathways

Organisms must adapt to environmental stresses to ensure their survival and prosperity. Different types of stresses, including thermal, mechanical, and hypoxic stresses, can alter the cellular state that accompanies changes in gene expression but not the cellular identity determined by a chromatin state that remains stable throughout life. Some tissues, such as adipose tissue, demonstrate remarkable plasticity and adaptability in response to environmental cues, enabling reversible cellular identity changes; however, the mechanisms underlying these changes are not well understood. We hypothesized that positive and/or negative "Integrators" sense environmental cues and coordinate the epigenetic and transcriptional pathways required for changes in cellular identity. Adverse environmental factors such as pollution disrupt the coordinated control contributing to disease development. Further research based on this hypothesis will reveal how organisms adapt to fluctuating environmental conditions, such as temperature, extracellular matrix stiffness, oxygen, cytokines, and hormonal cues by changing their cellular identities.

Associations between HIFs and tumor immune checkpoints: mechanism and therapy

Hypoxia, which activates a variety of signaling pathways to enhance tumor cell growth and metabolism, is among the primary features of tumor cells. Hypoxia-inducible factors (HIFs) have a substantial impact on a variety of facets of tumor biology, such as epithelial-mesenchymal transition, metabolic reprogramming, angiogenesis, and improved radiation resistance. HIFs induce hypoxia-adaptive responses in tumor cells. Many academics have presented preclinical and clinical research targeting HIFs in tumor therapy, highlighting the potential applicability of targeted HIFs. In recent years, the discovery of numerous pharmacological drugs targeting the regulatory mechanisms of HIFs has garnered substantial attention. Additionally, HIF inhibitors have attained positive results when used in conjunction with traditional oncology radiation and/or chemotherapy, as well as with the very promising addition of tumor immunotherapy. Immune checkpoint inhibitors (CPIs), which are employed in a range of cancer treatments over the past decades, are essential in tumor immunotherapy. Nevertheless, the use of immunotherapy has been severely hampered by tumor resistance and treatment-related toxicity. According to research, HIF inhibitors paired with CPIs may be game changers for multiple malignancies, decreasing malignant cell plasticity and cancer therapy resistance, among other things, and opening up substantial new pathways for immunotherapy drug development. The structure, activation mechanisms, and pharmacological sites of action of the HIF family are briefly reviewed in this work. This review further explores the interactions between HIF inhibitors and other tumor immunotherapy components and covers the potential clinical use of HIF inhibitors in combination with CPIs.

Multiplex Immunofluorescence Staining Protocol for the Dual Imaging of Hypoxia-Inducible Factors 1 and 2 on Formalin-Fixed Paraffin-Embedded Samples

Hypoxia is a common condition in rapidly proliferating tumors and occurs when oxygen delivery to the tissue is scarce. It is a prevalent feature in ~90% of solid tumors. The family of HIF (hypoxia-inducible factor) proteins-HIF1α and HIF2α-are the main transcription factors that regulate the response to hypoxia. These transcription factors regulate numerous downstream gene targets that promote the aggressiveness of tumors and therefore have been linked to worse prognosis in patients. This makes them a potential biomarker to be tested in the clinical setting to predict patient outcomes. However, HIFs have been notoriously challenging to immunolabel, in part due to their fast turnover under normal oxygen conditions. In this work, we developed a multiplexed immunofluorescence (mIF) staining protocol for the simultaneous detection of HIF1α and HIF2α in the same formalin-fixed paraffin-embedded (FFPE) tissue section.

Spontaneous metastasis xenograft models link CD44 isoform 4 to angiogenesis, hypoxia, EMT and mitochondria-related pathways in colorectal cancer

Hematogenous metastasis limits the survival of colorectal cancer (CRC) patients. Here, we illuminated the roles of CD44 isoforms in this process. Isoforms 3 and 4 were predominantly expressed in CRC patients. CD44 isoform 4 indicated poor outcome and correlated with epithelial-mesenchymal transition (EMT) and decreased oxidative phosphorylation (OxPhos) in patients; opposite associations were found for isoform 3. Pan-CD44 knockdown (kd) independently impaired primary tumor formation and abrogated distant metastasis in CRC xenografts. The xenograft tumors mainly expressed the clinically relevant CD44 isoforms 3 and 4. Both isoforms were enhanced in the paranecrotic, hypoxic tumor regions but were generally absent in lung metastases. Upon CD44 kd, tumor angiogenesis was increased in the paranecrotic areas, accompanied by reduced hypoxia-inducible factor-1α and CEACAM5 but increased E-cadherin expression. Mitochondrial genes and proteins were induced upon pan-CD44 kd, as were OxPhos genes. Hypoxia increased VEGF release from tumor spheres, particularly upon CD44 kd. Genes affected upon CD44 kd in xenografts specifically overlapped concordantly with genes correlating with CD44 isoform 4 (but not isoform 3) in patients, validating the clinical relevance of the used model and highlighting the metastasis-promoting role of CD44 isoform 4.

Staining Hypoxic Areas of Frozen and FFPE Tissue Sections with Hypoxyprobe™

Hypoxia occurs due to inadequate levels of oxygen in tissue and has been implicated in numerous diseases such as cancer, diabetes, cardiovascular, and neurodegenerative diseases. Hypoxia activates hypoxia-inducible factors (HIF) which mediate the expression of several downstream genes. Within the context of cancer biology, these genes affect cellular processes including metabolism, proliferation, migration, invasion, and metastasis. Pimonidazole hydrochloride (HCl) is an exogenous marker that is reduced and binds to thiols under hypoxic conditions resulting in adducts that can be visualized using antibodies such as Hypoxyprobe™. This chapter describes a method for using Hypoxyprobe™ to detect hypoxic areas in frozen and FFPE mouse samples by immunofluorescence (IF) and immunohistochemistry (IHC) staining.

KDM5A noncanonically binds antagonists MLL1/2 to mediate gene regulation and promotes epithelial to mesenchymal transition

Differential expression of genes involved in certain processes is a collaborative outcome of crosstalk between signalling molecules and epigenetic modifiers. In response to environmental stimulus, interplay between transcription factors and epigenetic modifiers together dictates the regulation of genes. MLLs and KDM5A are functionally antagonistic proteins, as one acts as a writer and the other erases the active chromatin mark, i.e., H3K4me3. KDM5A influences the process of EMT by binding to both epithelial and mesenchymal gene promoters. Through this work, we show that when bound to E-cadherin promoter, KDM5A acts as a classical repressor by demethylating H3K4me3, but on mesenchymal markers, it acts as a transcriptional activator by inhibiting the activity of HDACs and increasing H3K18ac. Further, through our chromatin immunoprecipitation experiments, we observed a co-occupancy of KDM5A with MLLs, we tested whether KDM5A might physically interact with MLLs and WDR5, and here we provide experimental evidence that KDM5A indeed interacts with MLLs and WDR5.

Histone deacetylase 3 deletion in alveolar type 2 epithelial cells prevents bleomycin-induced pulmonary fibrosis

BACKGROUND

Epithelial mesenchymal transformation (EMT) in alveolar type 2 epithelial cells (AT2) is closely associated with pulmonary fibrosis (PF). Histone deacetylase 3 (HDAC3) is an important enzyme that regulates protein stability by modulating the acetylation level of non-histones. Here, we aimed to explore the potential role and regulatory mechanisms associated with HDAC3 in PF.

METHODS

We quantified HDAC3 expression both in lung tissues from patients with PF and from bleomycin (BLM)-treated mice. HDAC3 was also detected in TGF-β1-treated AT2. The mechanistic activity of HDAC3 in pulmonary fibrosis and EMT was also explored.

RESULTS

HDAC3 was highly expressed in lung tissues from patients with PF and bleomycin (BLM)-treated mice, especially in AT2. Lung tissues from AT2-specific HDAC3-deficient mice stimulated with BLM showed alleviative fibrosis and EMT. Upstream of HDAC3, TGF-β1/SMAD3 directly promoted HDAC3 transcription. Downstream of HDAC3, we also found that genetic or pharmacologic inhibition of HDAC3 inhibited GATA3 expression at the protein level rather than mRNA. Finally, we found that intraperitoneal administration of RGFP966, a selective inhibitor of HDAC3, could prevent mice from BLM-induced pulmonary fibrosis and EMT.

CONCLUSION

TGF-β1/SMAD3 directly promoted the transcription of HDAC3, which aggravated EMT in AT2 and pulmonary fibrosis in mice via deacetylation of GATA3 and inhibition of its degradation. Our results suggest that targeting HDAC3 in AT2 may provide a new therapeutic target for the prevention of PF.

Targeting histone deacetylase-3 blocked epithelial-mesenchymal plasticity and metastatic dissemination in gastric cancer

BACKGROUND AND PURPOSE

Histone deacetylase (HDAC) inhibitors (HDIs) can modulate the epithelial-mesenchymal transition (EMT) progression and inhibit the migration and invasion of cancer cells. Emerging as a novel class of anti-cancer drugs, HDIs are attracted much attention in the field of drug discovery. This study aimed to discern the underlying mechanisms of Honokiol in preventing the metastatic dissemination of gastric cancer cells by inhibiting HDAC3 activity/expression.

EXPERIMENTAL APPROACH

Clinical pathological analysis was performed to determine the relationship between HDAC3 and tumor progression. The effects of Honokiol on pharmacological characterization, functional, transcriptional activities, organelle structure changes, and molecular signaling were analyzed using binding assays, differential scanning calorimetry, luciferase reporter assay, HDAC3 activity, ER stress response element activity, transmission electron microscopy, immune-blotting, and Wnt/β-catenin activity assays. The in vivo effects of Honokiol on peritoneal dissemination were determined by a mouse model and detected by PET/CT tomography.

KEY RESULTS

HDAC3 over-expression was correlated with poor prognosis. Honokiol significantly abolished HDAC3 activity (Y298) via inhibition of NFκBp65/CEBPβ signaling, which could be reversed by the over-expression of plasmids of NFκBp65/CEBPβ. Treatments with 4-phenylbutyric acid (a chemical chaperone) and calpain-2 gene silencing inhibited Honokiol-inhibited NFκBp65/CEBPβ activation. Honokiol increased ER stress markers and inhibited EMT-associated epithelial markers, but decreased Wnt/β-catenin activity. Suppression of HDAC3 by both Honokiol and HDAC3 gene silencing decreased cell migration and invasion in vitro and metastasis in vivo.

CONCLUSIONS AND IMPLICATIONS

Honokiol acts by suppressing HDAC3-mediated EMT and metastatic signaling. By prohibiting HDAC3, metastatic dissemination of gastric cancer may be blocked. Conceptual model showing the working hypothesis on the interaction among Honokiol, HDAC3, and ER stress in the peritoneal dissemination of gastric cancer. Honokiol targeting HDAC3 by ER stress cascade and mitigating the peritoneal spread of gastric cancer. Honokiol-induced ER stress-activated calpain activity targeted HDAC3 and blocked Tyr298 phosphorylation, subsequently blocked cooperating with EMT transcription factors and cancer progression. The present study provides evidence to demonstrate that HDAC3 is a positive regulator of EMT and metastatic growth of gastric cancer cells. The findings here imply that overexpressed HDAC3 is a potential therapeutic target for honokiol to reverse EMT and prevent gastric cancer migration, invasion, and metastatic dissemination. • Honokiol significantly abolished HDAC3 activity on catalytic tyrosine 298 residue site. In addition, Honokiol-induced ER stress markedly inhibited HDAC3 expression via inhibition of NFκBp65/CEBPβ signaling. • HDAC3, which is a positive regulator of metastatic gastric cancer cell growth, can be significantly inhibited by Honokiol. • Opportunities for HDAC3 inhibition may be a potential therapeutic target for preventing gastric cancer metastatic dissemination.

LncRNA AC142119.1 facilitates the progression of neuroblastoma by epigenetically initiating the transcription of MYCN

BACKGROUND

Oncogene MYCN is closely related with malignant progression and poor prognosis of neuroblastoma (NB). Recently, long non-coding RNAs (lncRNAs) have been recognized as crucial regulators in various cancers. However, whether lncRNAs contribute to the overexpression of MYCN in NB is unclear.

METHODS

Microarray analysis were applied to analyze the differentially expressed lncRNAs between MYCN-amplified and MYCN-non-amplified NB cell lines. Bioinformatic analyses were utilized to identify lncRNAs nearby MYCN locus. qRT-PCR was used to detect the expression level of lncRNA AC142119.1 in NB cell lines and tissues. Gain- and loss-of-function assays were conducted to investigate the biological effect of AC142119.1 in NB. Fluorescence in situ hybridization, RNA pull-down, RNA immunoprecipitation, mass spectrometry, RNA electrophoretic mobility shift, chromatin immunoprecipitation and chromatin isolation by RNA purification assays were performed to validate the interaction between AC142119.1 and WDR5 protein as well as MYCN promoter.

RESULTS

AC142119.1 was significantly elevated in NB tissues with MYCN amplification, advanced INSS stage and high risk, and associated with poor survival of NB patients. Moreover, enforced expression of AC142119.1 reinforced the proliferation of NB cells in vitro and in vivo. Additionally, AC142119.1 specifically recruited WDR5 protein to interact with MYCN promoter, further initiating the transcription of MYCN and accelerating NB progression.

CONCLUSIONS

We identified a novel lncRNA AC142119.1, which promoted the progression of NB through epigenetically initiating the transcription of MYCN via interacting with both WDR5 protein and the promoter of MYCN, indicating that AC142119.1 might be a potential diagnostic biomarker and therapeutic target for NB.

Hypoxia effects on oncolytic virotherapy in Cancer: Friend or Foe?

Researchers have tried to find novel strategies for cancer treatment in the past decades. Among the utilized methods, administering oncolytic viruses (OVs) alone or combined with other anticancer therapeutic approaches has had promising outcomes, especially in solid tumors. Infecting the tumor cells by these viruses can lead to direct lysis or induction of immune responses. However, the immunosuppressive tumor microenvironment (TME) is considered a significant challenge for oncolytic virotherapy in treating cancer. Based on OV type, hypoxic conditions in the TME can accelerate or repress virus replication. Therefore, genetic manipulation of OVs or other molecular modifications to reduce hypoxia can induce antitumor responses. Moreover, using OVs with tumor lysis capability in the hypoxic TME may be an attractive strategy to overcome the limitations of the therapy. This review summarizes the latest information available in the field of cancer virotherapy and discusses the dual effect of hypoxia on different types of OVs to optimize available related therapeutic methods.

E-box binding transcription factors in cancer

E-boxes are important regulatory elements in the eukaryotic genome. Transcription factors can bind to E-boxes through their basic helix-loop-helix or zinc finger domain to regulate gene transcription. E-box-binding transcription factors (EBTFs) are important regulators of development and essential for physiological activities of the cell. The fundamental role of EBTFs in cancer has been highlighted by studies on the canonical oncogene MYC, yet many EBTFs exhibit common features, implying the existence of shared molecular principles of how they are involved in tumorigenesis. A comprehensive analysis of TFs that share the basic function of binding to E-boxes has been lacking. Here, we review the structure of EBTFs, their common features in regulating transcription, their physiological functions, and their mutual regulation. We also discuss their converging functions in cancer biology, their potential to be targeted as a regulatory network, and recent progress in drug development targeting these factors in cancer therapy.

MiR-1236: Key controller of tumor development and progression: Focus on the biological functions and molecular mechanisms

Combating with the cancer, as one of the leading causes of morbidity and mortality worldwide, scientific community extensively evidenced microRNA 1236 (miR-1236) roles in the pathogenesis of malignant tumors. It has been mentioned that miR-1236 target genes and signal pathways that are key controller of tumor development and progression. Consistently, increasing evidence reports that miR-1236 participates in cancer cell growth, migration, invasion, apoptosis, and drug resistance, as well as tumor diagnosis, and prognosis. MiR-1236 is also implicated in epithelial-mesenchymal transition (EMT), which is a significant indicator of the metastatic process. Moreover, miR-1236 itself is regulated by several newly discovered long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs). Current review aimed to summarize and discuss different dimensions of miR-1236 involvement in the fundamental cellular and molecular mechanisms of tumor progressions. We believe that miR-1236 may serve as a non-invasive diagnostic marker and potential therapeutic target for cancer.

Epigenetic regulation of hybrid epithelial-mesenchymal cell states in cancer

Epithelial-to-mesenchymal transition (EMT) is a process by which cells lose their epithelial characteristics and gain mesenchymal phenotypes. In cancer, EMT is thought to drive tumor invasion and metastasis. Recent efforts to understand EMT biology have uncovered that cells undergoing EMT attain a spectrum of intermediate "hybrid E/M" states, which exist along an epithelial-mesenchymal continuum. Here, we summarize recent studies characterizing the epigenetic drivers of hybrid E/M states. We focus on the histone-modification writers, erasers, and readers that assist or oppose the canonical hybrid E/M transcription factors that modulate hybrid E/M state transitions. We also examine the role of chromatin remodelers and DNA methylation in hybrid E/M states. Finally, we highlight the challenges of targeting hybrid E/M pharmacologically, and we propose future directions that might reveal the specific and targetable mechanisms by which hybrid E/M drives metastasis in patients.

Single-cell RNA sequencing reveals microenvironment context-specific routes for epithelial-mesenchymal transition in pancreas cancer cells

In the PDAC tumor microenvironment, multiple factors initiate the epithelial-mesenchymal transition (EMT) that occurs heterogeneously among transformed ductal cells, but it is unclear if different drivers promote EMT through common or distinct signaling pathways. Here, we use single-cell RNA sequencing (scRNA-seq) to identify the transcriptional basis for EMT in pancreas cancer cells in response to hypoxia or EMT-inducing growth factors. Using clustering and gene set enrichment analysis, we find EMT gene expression patterns that are unique to the hypoxia or growth factor conditions or that are common between them. Among the inferences from the analysis, we find that the FAT1 cell adhesion protein is enriched in epithelial cells and suppresses EMT. Further, the receptor tyrosine kinase AXL is preferentially expressed in hypoxic mesenchymal cells in a manner correlating with YAP nuclear localization, which is suppressed by FAT1 expression. AXL inhibition prevents EMT in response to hypoxia but not growth factors. Relationships between FAT1 or AXL expression with EMT were confirmed through analysis of patient tumor scRNA-seq data. Further exploration of inferences from this unique dataset will reveal additional microenvironment context-specific signaling pathways for EMT that may represent novel drug targets for PDAC combination therapies.

Hypoxia as a regulator of tumor stroma and metastasis

Metastasis is the leading cause of mortality in most patients with cancer. Despite its clinical importance, mechanistic underpinnings of metastatic progression remain poorly understood. Hypoxia, a condition of insufficient oxygen availability, frequently occurs in solid tumors because of their high oxygen/nutrient demand and abnormal tumor vasculature. In this review, we describe the roles of hypoxia and hypoxia-inducible factor (HIF) signaling in the metastatic cascade, with an emphasis on recent biological insights from in vivo studies.

METTL4-mediated nuclear N6-deoxyadenosine methylation promotes metastasis through activating multiple metastasis-inducing targets

BACKGROUND

DNA N6-methyldeoxyadenosine (6mA) is rarely present in mammalian cells and its nuclear role remains elusive.

RESULTS

Here we show that hypoxia induces nuclear 6mA modification through a DNA methyltransferase, METTL4, in hypoxia-induced epithelial-mesenchymal transition (EMT) and tumor metastasis. Co-expression of METTL4 and 6mA represents a prognosis marker for upper tract urothelial cancer patients. By RNA sequencing and 6mA chromatin immunoprecipitation-exonuclease digestion followed by sequencing, we identify lncRNA RP11-390F4.3 and one novel HIF-1α co-activator, ZMIZ1, that are co-regulated by hypoxia and METTL4. Other genes involved in hypoxia-mediated phenotypes are also regulated by 6mA modification. Quantitative chromatin isolation by RNA purification assay shows the occupancy of lncRNA RP11-390F4.3 on the promoters of multiple EMT regulators, indicating lncRNA-chromatin interaction. Knockdown of lncRNA RP11-390F4.3 abolishes METTL4-mediated tumor metastasis. We demonstrate that ZMIZ1 is an essential co-activator of HIF-1α.

CONCLUSIONS

We show that hypoxia results in enriched 6mA levels in mammalian tumor cells through METTL4. This METTL4-mediated nuclear 6mA deposition induces tumor metastasis through activating multiple metastasis-inducing genes. METTL4 is characterized as a potential therapeutic target in hypoxic tumors.

Single-cell RNA sequencing uncovers a neuron-like macrophage subset associated with cancer pain

Tumor innervation is a common phenomenon with unknown mechanism. Here, we discovered a direct mechanism of tumor-associated macrophage (TAM) for promoting de novo neurogenesis via a subset showing neuronal phenotypes and pain receptor expression associated with cancer-driven nocifensive behaviors. This subset is rich in lung adenocarcinoma associated with poorer prognosis. By elucidating the transcriptome dynamics of TAM with single-cell resolution, we discovered a phenomenon "macrophage to neuron-like cell transition" (MNT) for directly promoting tumoral neurogenesis, evidenced by macrophage depletion and fate-mapping study in lung carcinoma models. Encouragingly, we detected neuronal phenotypes and activities of the bone marrow-derived MNT cells (MNTs) in vitro. Adoptive transfer of MNTs into NOD/SCID mice markedly enhanced their cancer-associated nocifensive behaviors. We identified macrophage-specific Smad3 as a pivotal regulator for promoting MNT at the genomic level; its disruption effectively blocked the tumor innervation and cancer-dependent nocifensive behaviors in vivo. Thus, MNT may represent a precision therapeutic target for cancer pain.

The WD repeat-containing protein 5 (WDR5) antagonist WDR5-0103 restores the efficacy of cytotoxic drugs in multidrug-resistant cancer cells overexpressing ABCB1 or ABCG2

The development of multidrug resistance (MDR) is one of the major challenges in the treatment of cancer which is caused by the overexpression of the ATP-binding cassette (ABC) transporters ABCB1 (P-glycoprotein) and/or ABCG2 (BCRP/MXR/ABCP) in cancer cells. These transporters are capable of reducing the efficacy of cytotoxic drugs by actively effluxing them out of cancer cells. Since there is currently no approved treatment for patients with multidrug-resistant tumors, the drug repurposing approach provides an alternative route to identify agents to reverse MDR mediated by ABCB1 and/or ABCG2 in multidrug-resistant cancer cells. WDR5-0103 is a histone H3 lysine 4 (H3K4) methyltransferase inhibitor that disrupts the interaction between the WD repeat-containing protein 5 (WDR5) and mixed-lineage leukemia (MLL) protein. In this study, the effect of WDR5-0103 on MDR mediated by ABCB1 and ABCG2 was determined. We found that in a concentration-dependent manner, WDR5-0103 could sensitize ABCB1- and ABCG2-overexpressing multidrug-resistant cancer cells to conventional cytotoxic drugs. Our results showed that WDR5-0103 reverses MDR and improves drug-induced apoptosis in multidrug-resistant cancer cells by inhibiting the drug-efflux function of ABCB1 and ABCG2, without altering the protein expression of ABCB1 or ABCG2. The potential sites of interactions of WDR5-0103 with the drug-binding pockets of ABCB1 and ABCG2 were predicted by molecular docking. In conclusion, the MDR reversal activity of WDR5-0103 demonstrated here indicates that it could be used in combination therapy to provide benefits to a subset of patients with tumor expressing high levels of ABCB1 or ABCG2.

RUNX Family in Hypoxic Microenvironment and Angiogenesis in Cancers

The tumor microenvironment (TME) is broadly implicated in tumorigenesis, as tumor cells interact with surrounding cells to influence the development and progression of the tumor. Blood vessels are a major component of the TME and are attributed to the creation of a hypoxic microenvironment, which is a common feature of advanced cancers and inflamed premalignant tissues. Runt-related transcription factor (RUNX) proteins, a transcription factor family of developmental master regulators, are involved in vital cellular processes such as differentiation, proliferation, cell lineage specification, and apoptosis. Furthermore, the RUNX family is involved in the regulation of various oncogenic processes and signaling pathways as well as tumor suppressive functions, suggesting that the RUNX family plays a strategic role in tumorigenesis. In this review, we have discussed the relevant findings that describe the crosstalk of the RUNX family with the hypoxic TME and tumor angiogenesis or with their signaling molecules in cancer development and progression.

Histone Deacetylase 3 Governs β-Estradiol-ERα-Involved Endometrial Tumorigenesis via Inhibition of STING Transcription

Purpose: The stimulator of interferon genes (STING) pathway plays a crucial role in antitumor immunity, and it is strictly regulated by many types of post-translational modifications. However, the contribution of acetylation involved in the regulation of STING to endometrial tumorigenesis remains unclear. Methods: We attempted to identify the key role of STING in endometrial carcinoma (EC) tissue and cell lines and explore its epigenetic regulation mechanism by HDACs that are critically involved in EC. We used IHC and qRT-PCR to detect the protein level and mRNA level of STING expression in endometrial carcinoma tissues, then explored the potential role of STING in tumor proliferation and apoptosis by CCK8 and flow cytometry, and identified the STING effect in the tumorigenicity by a mouse xenograft assay. We explored the possible relationship of acetylation alteration in STING regulation by ChIP analysis and Co-IP, and we knocked out STING in ECC1 and Ishikawa cells using CRISPR-Cas9 to further confirm the critical role of STING restoration induced by HDAC3 inhibitor RGFP-966 in the proliferation and apoptosis. Results: We found that STING expression was largely decreased and worked as an important regulator of cell proliferation and apoptosis; either activated or overexpressed STING, with both pharmacological and genetic approaches, largely blocked cell proliferation and induced apoptosis in EC. Moreover, STING expression was deregulated by both β-estradiol and HDAC3. Mechanically, we determined that HDAC3 can interact with β-estradiol-ERα and induce deacetylation of histone 3 lysine 4 at the STING promoter, thereby decreasing STING expression. Inhibition of HDAC3 increased STING expression, thereby inhibiting tumorigenesis. Conclusion: This study reveals a novel molecular mechanism by which HDAC3 inhibits STING transcription via β-estradiol-ERα and provides a promising therapy (a combination of HDAC and STING) for combating endometrial cancer.

Role of O-GlcNAcylation on cancer stem cells: Connecting nutrient sensing to cell plasticity

Tumor growth and metastasis can be promoted by a small sub-population of cancer cells, termed cancer stem-like cells (CSCs). While CSCs possess capability in self-renewing and differentiating, the hierarchy of CSCs during tumor growth is highly plastic. This plasticity in CSCs fate and function can be regulated by signals from the tumor microenvironment. One emerging pathway in CSCs that connects the alteration in microenvironment and signaling network in cancer cells is the hexosamine biosynthetic pathway (HBP). The final product of HBP, UDP-N-acetylglucosamine (UDP-GlcNAc), is utilized for glycosylating of membrane and secreted proteins, but also nuclear and cytoplasmic proteins by the post-translational modification O-GlcNAcylation. O-GlcNAcylation and its enzyme, O-GlcNAc transferase (OGT), are upregulated in nearly all cancers and been linked to regulate many cancer cell phenotypes. Recent studies have begun to connect OGT and O-GlcNAcylation to regulation of CSCs. In this review, we will discuss the emerging role of OGT and O-GlcNAcylation in regulating fate and plasticity of CSCs, as well as the potential in targeting OGT/O-GlcNAcylation in CSCs.

Gene regulation by histone-modifying enzymes under hypoxic conditions: a focus on histone methylation and acetylation

Oxygen, which is necessary for sustaining energy metabolism, is consumed in many biochemical reactions in eukaryotes. When the oxygen supply is insufficient for maintaining multiple homeostatic states at the cellular level, cells are subjected to hypoxic stress. Hypoxia induces adaptive cellular responses mainly through hypoxia-inducible factors (HIFs), which are stabilized and modulate the transcription of various hypoxia-related genes. In addition, many epigenetic regulators, such as DNA methylation, histone modification, histone variants, and adenosine triphosphate-dependent chromatin remodeling factors, play key roles in gene expression. In particular, hypoxic stress influences the activity and gene expression of histone-modifying enzymes, which controls the posttranslational modification of HIFs and histones. This review covers how histone methylation and histone acetylation enzymes modify histone and nonhistone proteins under hypoxic conditions and surveys the impact of epigenetic modifications on gene expression. In addition, future directions in this area are discussed.

New sequencing technologies are revealing how cells respond to hypoxia, insufficient oxygen, by managing gene activation. In multicellular organisms, gene activation is managed by how tightly a section of DNA is wound around proteins called histones; genes in tightly packed regions are inaccessible and inactive, whereas those in looser regions can be activated. Kyunghwan Kim, Sun-Ju Yi, and co-workers at Chungbuk National University in South Korea have reviewed recent data on how cells regulate gene activity under hypoxic conditions. Advances in sequencing technology have allowed genome-wide studies of how hypoxia affects DNA structure and gene activation, revealing that gene-specific modifications may be more important than genome-wide modifications. Hypoxia is implicated in several diseases, such as cancer and chronic metabolic diseases, and a better understanding of how it affects gene activation may help identify new treatments for hypoxia-related diseases.

The Promise of Targeting Hypoxia to Improve Cancer Immunotherapy: Mirage or Reality?

Almost all solid tumors display hypoxic areas in the tumor microenvironment associated with therapeutic failure. It is now well established that the abnormal growth of malignant solid tumors exacerbates their susceptibility to hypoxia. Therefore, targeting hypoxia remains an attractive strategy to sensitize tumors to various therapies. Tumor cell adaptions to hypoxia are primarily mediated by hypoxia-inducible factor-1 alpha (HIF-1α). Sensing hypoxia by HIF-1α impairs the apoptotic potential of tumor cells, thus increasing their proliferative capacity and contributing to the development of a chaotic vasculature in the tumor microenvironment. Therefore, in addition to the negative impact of hypoxia on tumor response to chemo- and radio-therapies, hypoxia has also been described as a major hijacker of the tumor response by impairing the tumor cell susceptibility to immune cell killing. This review is not intended to provide a comprehensive overview of the work published by several groups on the multiple mechanisms by which hypoxia impairs the anti-tumor immunity and establishes the immunosuppressive tumor microenvironment. There are several excellent reviews highlighting the value of targeting hypoxia to improve the benefit of immunotherapy. Here, we first provide a brief overview of the mechanisms involved in the establishment of hypoxic stress in the tumor microenvironment. We then discuss our recently published data on how targeting hypoxia, by deleting a critical domain in HIF-1α, contributes to the improvement of the anti-tumor immune response. Our aim is to support the current dogma about the relevance of targeting hypoxia in cancer immunotherapy.

Sirtuins and Hypoxia in EMT Control

Epithelial–mesenchymal transition (EMT), a physiological process during embryogenesis, can become pathological in the presence of different driving forces. Reduced oxygen tension or hypoxia is one of these forces, triggering a large number of molecular pathways with aberrant EMT induction, resulting in cancer and fibrosis onset. Both hypoxia-induced factors, HIF-1α and HIF-2α, act as master transcription factors implicated in EMT. On the other hand, hypoxia-dependent HIF-independent EMT has also been described. Recently, a new class of seven proteins with deacylase activity, called sirtuins, have been implicated in the control of both hypoxia responses, HIF-1α and HIF-2α activation, as well as EMT induction. Intriguingly, different sirtuins have different effects on hypoxia and EMT, acting as either activators or inhibitors, depending on the tissue and cell type. Interestingly, sirtuins and HIF can be activated or inhibited with natural or synthetic molecules. Moreover, recent studies have shown that these natural or synthetic molecules can be better conveyed using nanoparticles, representing a valid strategy for EMT modulation. The following review, by detailing the aspects listed above, summarizes the interplay between hypoxia, sirtuins, and EMT, as well as the possible strategies to modulate them by using a nanoparticle-based approach.

PHF13 epigenetically activates TGFβ driven epithelial to mesenchymal transition

Epigenetic alteration is a pivotal factor in tumor metastasis. PHD finger protein 13 (PHF13) is a recently identified epigenetic reader of H3K4me2/3 that functions as a transcriptional co-regulator. In this study, we demonstrate that PHF13 is required for pancreatic-cancer-cell growth and metastasis. Integrative analysis of transcriptome and epigenetic profiles provide further mechanistic insights into the epigenetic regulation of genes associated with cell metastasis during the epithelial-to-mesenchymal transition (EMT) induced by transforming growth factor β (TGFβ). Our data suggest PHF13 depletion impairs activation of TGFβ stimulated genes and correlates with a loss of active epigenetic marks (H3K4me3 and H3K27ac) at these genomic regions. These observations argue for a dependency of TGFβ target activation on PHF13. Furthermore, PHF13-dependent chromatin regions are enriched in broad H3K4me3 domains and super-enhancers, which control genes critical to cancer-cell migration and invasion, such as SNAI1 and SOX9. Overall, our data indicate a functional and mechanistic correlation between PHF13 and EMT.

Epithelial-mesenchymal transition in organ fibrosis development: current understanding and treatment strategies

Organ fibrosis is a process in which cellular homeostasis is disrupted and extracellular matrix is excessively deposited. Fibrosis can lead to vital organ failure and there are no effective treatments yet. Although epithelial–mesenchymal transition (EMT) may be one of the key cellular mechanisms, the underlying mechanisms of fibrosis remain largely unknown. EMT is a cell phenotypic process in which epithelial cells lose their cell-to-cell adhesion and polarization, after which they acquire mesenchymal features such as infiltration and migration ability. Upon injurious stimulation in different organs, EMT can be triggered by multiple signaling pathways and is also regulated by epigenetic mechanisms. This narrative review summarizes the current understanding of the underlying mechanisms of EMT in fibrogenesis and discusses potential strategies for attenuating EMT to prevent and/or inhibit fibrosis. Despite better understanding the role of EMT in fibrosis development, targeting EMT and beyond in developing therapeutics to tackle fibrosis is challenging but likely feasible.

WIN site inhibition disrupts a subset of WDR5 function

WDR5 nucleates the assembly of histone-modifying complexes and acts outside this context in a range of chromatin-centric processes. WDR5 is also a prominent target for pharmacological inhibition in cancer. Small-molecule degraders of WDR5 have been described, but most drug discovery efforts center on blocking the WIN site of WDR5, an arginine binding cavity that engages MLL/SET enzymes that deposit histone H3 lysine 4 methylation (H3K4me). Therapeutic application of WIN site inhibitors is complicated by the disparate functions of WDR5, but is generally guided by two assumptions-that WIN site inhibitors disable all functions of WDR5, and that changes in H3K4me drive the transcriptional response of cancer cells to WIN site blockade. Here, we test these assumptions by comparing the impact of WIN site inhibition versus WDR5 degradation on H3K4me and transcriptional processes. We show that WIN site inhibition disables only a specific subset of WDR5 activity, and that H3K4me changes induced by WDR5 depletion do not explain accompanying transcriptional responses. These data recast WIN site inhibitors as selective loss-of-function agents, contradict H3K4me as a relevant mechanism of action for WDR5 inhibitors, and indicate distinct clinical applications of WIN site inhibitors and WDR5 degraders.

Stress Responses as Master Keys to Epigenomic Changes in Transcriptome and Metabolome for Cancer Etiology and Therapeutics

From initiation through progression, cancer cells are subjected to a magnitude of endogenous and exogenous stresses, which aid in their neoplastic transformation. Exposure to these classes of stress induces imbalance in cellular homeostasis and, in response, cancer cells employ informative adaptive mechanisms to rebalance biochemical processes that facilitate survival and maintain their existence. Different kinds of stress stimuli trigger epigenetic alterations in cancer cells, which leads to changes in their transcriptome and metabolome, ultimately resulting in suppression of growth inhibition or induction of apoptosis. Whether cancer cells show a protective response to stress or succumb to cell death depends on the type of stress and duration of exposure. A thorough understanding of epigenetic and molecular architecture of cancer cell stress response pathways can unveil a plethora of information required to develop novel anticancer therapeutics. The present view highlights current knowledge about alterations in epigenome and transcriptome of cancer cells as a consequence of exposure to different physicochemical stressful stimuli such as reactive oxygen species (ROS), hypoxia, radiation, hyperthermia, genotoxic agents, and nutrient deprivation. Currently, an anticancer treatment scenario involving the imposition of stress to target cancer cells is gaining traction to augment or even replace conventional therapeutic regimens. Therefore, a comprehensive understanding of stress response pathways is crucial for devising and implementing novel therapeutic strategies.

Epigenetic Regulation During Hypoxia and Its Implications in Cancer

Hypoxia is defined as a cellular stress condition caused by a decrease in oxygen below physiologically normal levels. Cells in the core of a rapidly growing solid tumor are faced with the challenge of inadequate supply of oxygen through the blood, owing to improper vasculature inside the tumor. This hypoxic microenvironment inside the tumor initiates a gene expression program that alters numerous signaling pathways, allowing the cancer cell to eventually evade adverse conditions and attain a more aggressive phenotype. A multitude of studies covering diverse aspects of gene regulation has tried to uncover the mechanisms involved in hypoxia-induced tumorigenesis. The role of epigenetics in executing widespread and dynamic changes in gene expression under hypoxia has been gaining an increasing amount of support in recent years. This chapter discusses, in detail, various epigenetic mechanisms driving the cellular response to hypoxia in cancer.

Histone Deacetylase 3: A Potential Therapeutic Target for Atherosclerosis

Atherosclerosis, the pathological basis of most cardiovascular disease, is characterized by plaque formation in the intima. Secondary lesions include intraplaque hemorrhage, plaque rupture, and local thrombosis. Vascular endothelial function impairment and smooth muscle cell migration lead to vascular dysfunction, which is conducive to the formation of macrophage-derived foam cells and aggravates inflammatory response and lipid accumulation that cause atherosclerosis. Histone deacetylase (HDAC) is an epigenetic modifying enzyme closely related to chromatin structure and gene transcriptional regulation. Emerging studies have demonstrated that the Class I member HDAC3 of the HDAC super family has cell-specific functions in atherosclerosis, including 1) maintenance of endothelial integrity and functions, 2) regulation of vascular smooth muscle cell proliferation and migration, 3) modulation of macrophage phenotype, and 4) influence on foam cell formation. Although several studies have shown that HDAC3 may be a promising therapeutic target, only a few HDAC3-selective inhibitors have been thoroughly researched and reported. Here, we specifically summarize the impact of HDAC3 and its inhibitors on vascular function, inflammation, lipid accumulation, and plaque stability in the development of atherosclerosis with the hopes of opening up new opportunities for the treatment of cardiovascular diseases.

Hypoxia signaling pathway: A central mediator in endocrine tumors

Adequate oxygen levels are essential for the functioning and maintenance of biological processes in virtually every cell, albeit based on specific need. Thus, any change in oxygen pressure leads to modulated activation of the hypoxia pathway, which affects numerous physiological and pathological processes, including hematopoiesis, inflammation, and tumor development. The Hypoxia Inducible Factors (HIFs) are essential transcription factors and the driving force of the hypoxia pathway; whereas, their inhibitors, HIF prolyl hydroxylase domain (PHDs) proteins are the true oxygen sensors that critically regulate this response. Recently, we and others have described the central role of the PHD/HIF axis in various compartments of the adrenal gland and its potential influence in associated tumors, including pheochromocytomas and paragangliomas. Here, we provide an overview of the most recent findings on the hypoxia signaling pathway in vivo, including its role in the endocrine system, especially in adrenal tumors.

Human Cytomegalovirus Egress: Overcoming Barriers and Co-Opting Cellular Functions

The assembly of human cytomegalovirus (HCMV) and other herpesviruses includes both nuclear and cytoplasmic phases. During the prolonged replication cycle of HCMV, the cell undergoes remarkable changes in cellular architecture that include marked increases in nuclear size and structure as well as the reorganization of membranes in cytoplasm. Similarly, significant changes occur in cellular metabolism, protein trafficking, and cellular homeostatic functions. These cellular modifications are considered integral in the efficient assembly of infectious progeny in productively infected cells. Nuclear egress of HCMV nucleocapsids is thought to follow a pathway similar to that proposed for other members of the herpesvirus family. During this process, viral nucleocapsids must overcome structural barriers in the nucleus that limit transit and, ultimately, their delivery to the cytoplasm for final assembly of progeny virions. HCMV, similar to other herpesviruses, encodes viral functions that co-opt cellular functions to overcome these barriers and to bridge the bilaminar nuclear membrane. In this brief review, we will highlight some of the mechanisms that define our current understanding of HCMV egress, relying heavily on the current understanding of egress of the more well-studied α-herpesviruses, HSV-1 and PRV.